Lordotic interbody spinal fusion implants

ABSTRACT

The present application is directed to interbody spinal fusion implants having a structural configuration that provides for the maintaining and creating of the normal anatomic angular relationship of two adjacent vertebrae of the spine to maintain and create spinal lordosis. The spinal fusion implants are sized to fit within the disc space created by the removal of disc material between two adjacent vertebrae and conform wholly or in part to the disc space created. The spinal fusion implants of the present invention have upper and lower surfaces that form a support structure for bearing against the end plates of the adjacent vertebrae. The upper and lower surfaces are disposed in a converging angular relationship to each other such that the implants have an overall “wedged-shape” in an elevational side view. The angular relationship of the upper and lower surfaces places and maintains the vertebrae adjacent to those surfaces in an angular relationship to each other, creating and maintaining the desired lordosis.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/813,283filed Mar. 10, 1997, now U.S. Pat. No. 6,302,914, which is a divisionalof application Ser. No. 08/482,146 filed Jun. 7, 1995, now U.S. Pat. No.5,609,635.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to interbody spinal fusionimplants, and in particular to spinal fusion implants configured torestore and maintain two adjacent vertebrae of the spine in correctanatomical angular relationship.

2. Description of The Related Art

Both the cervical and lunbar areas of the human spine are, in a healthystate, lordotic such that they are curved convex forward. It is notuncommon that in degenerative conditions of the spine that lordosis islost. This effectively shortens the spinal canal which decreases itscapacity. Further, the absence of lordosis moves the spinal cordanteriorly where it may be compressed against the posterior portions ofthe vertebral bodies and discs. Finally, such a loss of lordosisdisturbs the overall mechanics of the spine which may cause cascadingdegenerative changes throughout the adjacent spinal segments.

The surgical treatment of those degenerative conditions of the spine inwhich the spinal discs are in various states of collapse, and out oflordosis, commonly involves spinal fusion. That is the joining togetherof adjacent vertebrae through an area of shared bone. When the sharedbone is in the area previously occupied by the intervertebral disc thatis referred to as an interbody fusion. Further history in this regard isprovided in application Ser. No. 08/263,952 entitled Artificial SpinalFusion Implants (“Parent Application”) incorporated herein by reference.

The Parent Application taught the use of artificial spinal fusionimplants that were capable of being placed between adjacent vertebrae,and which implants were capable of containing and providing fusionpromoting substances including bone at the fusion site. These deviceswere further capable of restoring the height of the disc space and ofsupporting the spine, and were self-stabilizing as well as beingstabilizing to the spinal area where implanted.

SUMMARY OF THE INVENTION

The present invention is directed to interbody spinal fusion implantshaving a structural configuration that provides for the maintaining andcreating of the normal anatomic angular relationship of two adjacentvertebrae of the spine to maintain and create spinal lordosis. Thespinal fusion implants of the present invention are sized to fit withinthe disc space created by the removal of disc material between twoadjacent vertebrae and conform wholly or in part to the disc spacecreated. The spinal fusion implants of the present invention have upperand lower surfaces that form a support structure for bearing against theend plates of the adjacent vertebrae. In the preferred embodiments, theupper and lower surfaces are disposed in a converging angularrelationship to each other such that the implants of the presentinvention have an overall “wedged-shape” in an elevational side view.The angular relationship of the upper and lower surfaces places andmaintains the vertebrae adjacent to those surfaces in an angularrelationship to each other, creating and maintaining the desiredlordosis.

The implants of the present invention may have surface irregularities toincrease their surface area, and/or to further engage the adjacentvertebrae and to enhance stability. The lordotic implants of the presentinvention may have surface irregularities that are uniform in heightalong the longitudinal axis of the upper and lower vertebrae engagingsurfaces, or may increase in height from one end of the implant to theother. That is, the implant body and the surface formed and theprojections may be similarly wedged. The outer contour of the surfaceprojections may be more or less rectangular while the underlying implantmay be wedge-shaped; or the reverse wherein the underlying implant bodyis more or less rectangular while the contour of the surface projectionsare wedge-shaped from one end of the implant to the other.

The implants of the present invention have various faces which may becurved so as to conform to the shape of the vertebral surfaces adjacentto the area of the disc removal. Specifically the upper and/or lowersurfaces may be convex, and/or the front and/or rear surfaces may beconvex. The surfaces of the implants of the present invention may haveopenings which may or may not pass all the way through them, and acentral chamber in communication to the surface through holes. Theopenings may be of random sizes, and/or shapes, and/or distributions.The implants themselves may be composed of materials, and/or havesurface treatments, to encourage microscopic bone ingrowth into theimplants.

In the performing of a posterior lumbar interbody fusion, it is notpossible to replace the removed portions of the disc, if a total nucleardiscectomy has been performed, with a single large implant as thedelicate dural sac containing the spinal cord, and the nerve roots coverat all times at least some portion of the posterior disc space. As setforth in the Parent Application, the use of “modular implants” isappropriate in such cases. The modular implants being approximately aslong as the depth of the disc material removed, but being considerablynarrower, such that they can be introduced into the disc space from theposterior aspect to either side of the dural sac, and then aligned sideto side within the disc space so that a number of them each having alength consistent with the depth of the disc removed in that area wouldin combination have a width equal to the width of the disc materialremoved.

The modular implants of the present invention may be generallywedge-shaped and may have upper and lower surfaces conforming to thecontours of the vertebral endplates, which contours include but are notlimited to being relatively flat or convex. As the disc spaces in thelumbar spine are generally lordotic, said implants in the preferredembodiment would be taller anteriorly, that is at the implant'sinsertion end, and less tall posteriorly, that is at the implant'strailing end. To introduce an implant that is taller at its insertionend than the space available at the posterior aspect of the disc space,even when that disc space is optimally distracted, is problematic.

The modular implants of the present invention provide two solutions tothe problem. In the first embodiment, the modular implants may have areduced size at their insertion end, including but not limited to abullet nose, a convexity, and a chamfer to a smaller front surface. Thisthen provides that the implant has an area small enough to be introducedinto the posterior aspect of the disc space when the disc space isadequately distracted and the contour of that specialized leadingportion of the implant is such that it then allows for a ramping up ofthe adjacent vertebrae relative to the implant as the implant isadvanced forward into the disc space.

The implants of the present invention provide a second solution to thissame problem. In the preferred embodiment of the modular implant, theimplant is again wedge-shaped in the side elevational view and is tallerat its insertion end than at its trailing end. flowever, the implantincorporates at its trailing end a means for engaging insertioninstrumentation such as the box and threaded opening configurationdisclosed in the Parent Application. Since in the preferred embodimentthese implants are wedge-shaped in the side elevational view whenupright but are generally rectangular when viewed from the top planview, these implants are therefore designed to be introduced into thedisc space on their side such that the side walls of the implants areadjacent to the end plates of the adjacent vertebrae. The implants havea side-to-side dimension that is less than the dimension through theinsertion end of the implant when upright. It is possible to easilyinsert these implants with them on their side and then to use theinsertion instrument engaged to the implant to rotate the implantsninety degrees into the fully upright position, once they have beenfully inserted. Once inserted, the upper and lower surfaces are adjacentto the endplates of the adjacent vertebrae and create and maintain thedesired angular relationship of the adjacent vertebrae as the upper andlower walls are angled with respect to each other.

In an alternative embodiment of the present invention, a mechanicalimplant which may be inserted in a collapsed position and which may thenbe adjusted to increase in height so as to provide for the optimalrestoration of the height of the space between the adjacent vertebrae isdisclosed. The mechanical implant may be wedge-shaped, and have upperand lower surfaces, the contours of which generally conform to thecontacted areas of the adjacent vertebral endplates and which contoursmay include but are not limited to being relatively flat, or convex.Further, the mechanical implant may be wedge-shaped or generallyrectangular, but capable of increasing in both height and the extent ofwedging when adjusted. This may easily be achieved by having one of thetwo wedge mechanisms employed in the example given being larger, orsteeper than the other. Alternatively, a single wedge may be utilized,and if it is desired to achieved increased height at one end of theimplant while restricting the height at the other, then the end of theimplant may incorporate a hinge means and the height expansion at theother end achieved by drawing a wedge member, bar, ball, or other meansfrom the far end toward the hinged end so as to drive said upper andlower surfaces apart in a wedged fashion.

In an alternative embodiment of the present invention, an implant havinga mechanically deployable bone engaging means is taught. Such an implantis generally wedge-shaped in the side elevational view and has upper andlower surfaces generally conforming to the contour of the vertebralendplates where contacted by the implant, and which upper and lowersurfaces may be but are not limited to being either flat or convex. Theuse of such deployable bone engaging means are particularly of value inthat the largest possible implant may be inserted into a disc space andthe vertebral engaging means, which if fixed to the surface would haveblocked the insertion of the implant, may then be deployed after theinsertion such that the distance from the tip of the upper and lowerboite engagement means exceeds the height of the space available forinsertion. Such a feature is of particular value when the implant itselfis wedge-shaped as the considerable compressive loads across the lumbarspine would tend to drive a wedge-shaped implants out of the disc space.

OBJECTS OF THE PRESENT INVENTION

It is an object of the present invention to provide a spinal fusionimplant that is easily inserted into the spine, having a tapered leadingend;

It is another object of the present invention to provide a spinal fusionimplant that tapers in height from one end to the other consistent withthe taper of a normal spinal disc;

It is yet another object of the present invention to provide a spinalfusion implant that is capable of maintaining anatomic alignment andlordosis of two adjacent vertebrae during the spinal fusion process;

It is still another object of the present invention to provide a spinalfusion implant that is self stabilizing within the spine;

It is yet another object of the present invention to provide a spinalfusion. implant that is capable of providing stability between adjacentvertebrae when inserted;

It is further another object of the present invention to provide aspinal fusion implant that is capable of spacing apart and supportingadjacent vertebrae in an angular relationship during the spinal fusionprocess;

It is still further another object of the present invention to provide aspinal fusion implant that fits between to adjacent vertebrae andpreserves the end plants of those vertebrae; and

It is another object of the present invention to provide a spinal fusionimplant having a shape which conforms to the endplates of the adjacentvertebrae; and

These and other objects of the present invention will become apparentfrom a review of the accompanying drawings and the detailed descriptionof the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the lordotic interbody spinal fusionimplant of the present invention with a slidable door shown in apartially open position providing access to the internal chamber of theimplant.

FIG. 2 is a top plan view of the lordotic interbody spinal fusionimplant of the present invention.

FIG. 3 is a left side elevational view of the lordotic interbody spinalfusion implant of the present invention.

FIG. 4 is a right side elevational view of the lordotic interbody spinalfusion implant of the present invention.

FIG. 5 is a front end view of the lordotic interbody spinal fusionimplant of the present invention showing the slidable door in apartially open position.

FIG. 6 is a rear end view of the lordotic interbody spinal fusionimplant of the present invention showing the means for engaginginsertion instrumentation.

FIG. 7 is an enlarged fragmentary view along line 7 of FIG. 2illustrating the bone engaging surface configuration of the lordoticinterbody spinal fusion implant of the present invention.

FIG. 7A is an elevational side view of a segment of the spinal columnhaving the lordotic implant of the present invention inserted in thedisc space at different disc levels between adjacent vertebrae torestore and maintain the correct anatomical alignment of the adjacentvertebrae.

FIG. 8 is a top plan view of an alternative embodiment of the lordoticinterbody spinal fusion implant of the present invention.

FIG. 9 is a left side elevational view of the lordotic interbody spinalfusion implant of FIG. 8.

FIG. 10 is a front end view of the lordotic interbody spinal fusionimplant of FIG. 8.

FIG. 11 is a rear end view of the lordotic interbody spinal fusionimplant of FIG. 8 showing the means for engaging insertioninstrumentation.

FIG. 12 is an enlarged fragmentary view along line 12 of FIG. 8illustrating the surface configuration the lordotic interbody spinalfusion implant of the present invention.

FIG. 13 is a top plan view of an alternative embodiment of the lordoticinterbody spinal fusion implant of the present invention made of amesh-like material.

FIG. 14 is a left side elevational view of the lordotic interbody spinalfusion implant of FIG. 13.

FIG. 15 is a front end view of the lordotic interbody spinal fusionimplant of FIG. 13.

FIG. 16 is a rear end view of the lordotic interbody spinal fusionimplant of FIG. 13 showing the means for engaging insertioninstrumentation.

FIG. 17 is an enlarged fragmentary view along line 17 of FIG. 13illustrating the surface configuration of the lordotic interbody spinalfusion implant of the present invention.

FIG. 18 is a perspective view of an alternative embodiment of thelordotic interbody spinal fusion implant of the present invention.

FIG. 19 is a top plan view of the lordotic interbody spinal fusionimplant of FIG. 18.

FIG. 20 is a left side elevational view of the lordotic interbody spinalfusion implant of FIG. 18.

FIG. 21 is a rear end view of the lordotic interbody spinal fusionimplant of FIG. 18.

FIG. 22 is a front end view of the lordotic interbody spinal fusionimplant of FIG. 18.

FIG. 23 is an enlarged fragmentary view along line 23 of FIG. 22illustrating the surface configuration the lordotic interbody spinalfusion implant of the present invention.

FIG. 24 is a top plan view of an alternative embodiment of the lordoticinterbody spinal fusion implant of the present invention.

FIG. 25 is a left side elevational view of the lordotic interbody spinalfusion implant of FIG. 24.

FIG. 26 is a rear end view of the lordotic interbody spinal fusionimplant of FIG. 24.

FIG. 27 is a front end view of the lordotic interbody spinal fusionimplant of FIG. 24.

FIG. 28 is an enlarged fragmentary view along line 28 of the lordoticinterbody spinal fusion implant of FIG. 24 illustrating the surfaceconfiguration of the lordotic interbody spinal fusion implant of thepresent invention.

FIG. 29 is a sectional view along lines 29—29 of FIG. 28 the lordoticinterbody spinal fusion implant of the present invention.

FIG. 30 is a side elevational view of a segment of the human spinalcolumn shown with an alternative embodiment of the lordotic spinalfusion implant of the present invention that is adjustable andexpandable shown in sectional view inserted in the disc space levels torestore and maintain the correct anatomical alignment of the adjacentvertebrae.

FIG. 31 is a side cross sectional view of, an alternative embodiment ofthe lordotic implant of the present invention having movableprojections, in the form of spikes 708, which are movable from a firstposition within the implant 700 to a second position extending to theexterior of the implant.

FIG. 32 is a perspective view of the embodiment of FIG. 31.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1 through 7 the lordotic interbody spinal fusionimplant of the present invention for use in the disc space between twoadjacent vertebrae, generally referred to by the numeral 100, is shown.The implant 100 has a generally rectangular configuration, having anupper surface 112 and a lower surface 114. In the preferred embodiment,the upper and lower surfaces 112 and 114 of implant 100 are disposed ina converging angular relationship toward each other such that theimplant 100 appears “wedge-shaped” from a side elevational view as shownin FIGS. 3 and 4. The upper and lower surfaces 112 and 114 have aninterior surface which form a support structure for bearing against theendplates of the adjacent vertebrae between which the implant 100 isinserted. The angular relationship of the upper and lower surfaces 112and 114 places and maintains the vertebrae adjacent to those surfaces inan angular relationship, creating and maintaining the desired lordosisof the spine.

The upper and lower surfaces 112 and 114 of the implant 100 may be flator curved to conform to the shape of the end plates of the adjacentvertebrae between which the implant 100 is inserted. The implant 100conforms to the shape of the nucleus pulposus and a portion of theannulus fibrosus removed from the vertebrae. The upper and lowersurfaces 112 and 114 comprise surface roughenings that provide a surfacesuitable for engaging the adjacent vertebrae to stabilize the implant100 within the disc space once surgically implanted. The surfaceroughenings of the upper and lower surfaces 112 and 114 comprise asurface knurling 121 and/or grooves.

Referring to FIG. 7, an enlarged fragmentary view of the surfaceknurling 121 of the implant 100 is shown as a diamond-shaped boneengaging pattern. The implant 100 may have surface knurling 121throughout the entire upper and lower surfaces 112 and 114, throughoutonly a portion of the upper and lower surfaces 112 and 114, or anycombination thereof, without departing from the scope of the presentinvention. It is also appreciated that the surface knurling 121 may havevarious configuration other than the configuration shown.

In this embodiment, the implant 100 is hollow and comprises a pluralityof openings 115 of passing through the upper and lower surfaces 112 and114 and into a central hollow chamber 116. The openings 115 provide forbone growth to occur from the vertebrae through the openings 115 to theinternal chamber 116. While the openings 115 have been shown in thedrawings as being circular, it is appreciated that the openings 115 mayhave any shape, size, configuration or distribution suitable for use ina spinal implant without departing from the scope of the presentinvention. For example, the openings may have a tear-drop configurationas shown in opening 115 a in FIGS. 1 and 2. The upper and lower surfaces112 and 114 of the implant 100 are supported and spaced apart by a sidewall 118, which may also comprise a plurality of openings 122.

The implant 100 has an insertion end 120 and a trailing end 130 both ofwhich may be curved or flat. The trailing end 130 of the implant may beconvex to conform to the curvature of the vertebrae and has a means forengaging an implant insertion instrument comprising a depressed portion124 with a central threaded opening 126 for receiving the engaging endof a driving instrument. The insertion end 120 of the implant 100comprises an access opening 132 and a slidable door 134 which closes theopening 132. The slidable door 134 covers the opening 132 into thechamber 116 and permits the insertion of autogenous bone material intothe chamber 116.

In use, the slidable door 134 is placed in the open position for loadingmaterial into the chamber 116. The slideable door 134 has a depression136 for facilitating the opening and closing of the door 134. Theinternal chamber 116 can be filled and hold any natural or artificialosteoconductive, osteoinductive, osteogenic, or other fusion enhancingmaterial. Some examples of such materials are bone harvested from thepatient, or bone growth inducing material such as, but not limited to,hydroxyapatite, hydroxyapatite tricalcium phosphate; or bone morphogenicprotein. The implant 100 itself is made of material appropriate forhuman implantation such as titanium and/or may be made of, and/or filledand/or coated with a bone ingrowth inducing material such as, but notlimited to, hydroxyapatite or hydroxyapatite tricalcium phosphate or anyother osteoconductive, osteoinductive, osteogenic, or other fusionenhancing material.

The fusion enhancing material that is packed within the chamber 116 ofthe implant 100 serves to promote bone ingrowth between the implant 100and the adjacent vertebrae. Once the bone ingrowth occurs, the implant100 will be a permanent fixture preventing dislodgement of the implantas well as preventing any movement between the adjacent vertebrae.

The slidable door 134 is then closed prior to implantation. In theclosed position, the slideable door conforms to the curvature of theinsertion end 120 of the implant 100. Various methods of packing theimplant 100 with the autogenous bone material may be used to obtain acompletely packed implant 100.

The method of inserting the implant 100 is set forth in detail inapplication Ser. No. 08/263,952, incorporated herein by reference. Thethreaded end of a driving instrument is attached to the threaded opening126 in the trailing end 130 of the implant 100 and the fitting of thedriving instrument into the depressed portion 124 prevents movement ofthe implant 100 in relationship to the driving instrument. The implant100 is then placed at the entrance to the disc space between the twoadjacent vertebrae V. The driver instrument is then tapped with a hammersufficiently hard enough to drive the implant 100 into the disc space.

The size of the implant 100 is substantially the same size as the discmaterial that it is replacing and thus will be larger or smallerdepending on the amount of disc material removed to create the discspace in which it is to be used. In the preferred embodiment in regardto the lumbar spine the implant 100 has a width W approximately 28-48 mmwide, approximately 36 mm being preferred. The implant 100 has a heightH conforming to the restoration of the anatomic height of the disc spacethe average height would range from 8-16 mm, with 10-12 of which beingthe preferred average height. The depth D along mid-longitudinal axisMLA would at its maximum range from 20 to 34 mm with 26 to 32 being thepreferred maximum depth. In the cervical spine the width of the implantis in the range of approximately 14-28 mm, with the preferred widthbeing 18-22 mm. The implant has a height in the range of approximately5-10 mm with the preferred height being 6-8 mm. The implant has a depthin the range of approximately 11-21 mm with the preferred depth being11-13 mm.

Referring to FIG. 7A, a side elevational view of the lateral aspect of asegment of the spinal column S is shown with the implant 100 inserted inthe disc space D₂ between two adjacent vertebrae V₂ and V₃. The implant100 is inserted in the direction of arrow A into the disc space D₂ andmaintains the two vertebrae V₂ and V₃ in angular relationship to eachother such that the natural lordosis of that segment of the spinalcolumn S is restored. The forward advancement of the implant 100 isblocked by the natural bone processes B in the endplates of thevertebrae V₂ and V₃. Backing out of the implant 100 is prevented by thebone engaging surface knurling 121 of the upper and lower surfaces 112and 114.

Referring to FIGS. 8-12, an alternative embodiment of the lordoticinterbody spinal fusion implant of the present invention, generallyreferred to by the numeral 200, is shown. The implant 200 has a similaroverall configuration as the implant 100 described above. In thepreferred embodiment, the implant 200 is solid and comprises a pluralityof channels 215 passing from the upper surface 212 to the lower surface214 through the implant 200. The channels 215 provide for bone ingrowthand facilitate the incorporation of the implant 200 into the spinalfusion mass. The channels may also be loaded with fusion promotingmaterials such as those described above, prior to implantation. It isappreciated that the channels 215 need not pass all the way through theimplant 200, but can have a configuration similar to wells, which mayhold fusion promoting materials and permit bone ingrowth into the upperand lower surfaces 212 and 214 of the implant 200.

In addition to the channels 215, the implant 200 may have small openings222 on the side wall 218 which may or may not pass through the entireimplant 200. The same openings 222 may be in communication with thechannels 215 such that bone ingrowth may occur from the openings 222 tothe channels 215 to lock the implant 200 into the fusion mass. If theopenings 222 do not pass through the entire implant 200, they mayfunction as small wells for holding fusion promoting materials ordescribed above.

In the preferred embodiment of implant 200, the channels 215 have adiameter in the range of 0.1 mm to 6 mm, with 2-3 mm being the preferreddiameter. The openings 222 have a diameter in the range of 0.1 mm to 6mm, with 1-3 mm being the preferred diameter range. It is appreciatedthat although the channels 215 and openings 222 are shown having agenerally rounded configuration, it is within the scope of the presentinvention that the channels 215 and openings 222 may have any size,shape, configuration, and distribution suitable for the intendedpurpose.

The implant 200, has a plurality of ratchetings 250 on the upper andlower surface 212 and 214 for engaging the bone of the adjacentvertebrae. The ratchetings 250 comprise a bone engaging edge 252 andangled segment 254.

Referring specifically to FIG. 9, the implant 200 has a wedge-shapedelevational side view in which the trailing end 230 is taller than theinsertion end 220. The plurality of ratchetings 250 are oriented in thedirection of the insertion end 220 to provide for a one-way insertion ofthe implant 200 as the bone engaging edge 252, or ridge, engages thevertebrae and prevents the implant from backing out once implanted.Alternatively, the trailing end ratchetings could be of a lessor heightsuch that the overall shape of the ratchetings as a group is convex.

Referring to FIG. 11, the trailing end 230 of implant 200 has means forengaging insertion instrumentation comprising a thread opening 226 asdescribed above for implant 100.

Referring to FIG. 12, an enlarged fragmentary view along line 12 of FIG.8 illustrating the surface configuration the implant 200 is shown. Theupper and lower surfaces 212 and 214 of implant 200, in addition to theratcheting 250 comprise a porous texture 260 to present an irregularsurface to the bone to promote bone ingrowth. The porous texture 260 isalso able to hold fusion promoting materials and provides for anincreased surface area to engage the bone in the fusion process and toprovide further stability. The porous texture 260 may also be present onthe side walls 218. It is appreciated that the outer surface and/or theentire implant 200, may comprise any other porous material or roughenedsurface sufficient to hold fusion promoting substances and/or allow forbone ingrowth and/or engage the bone during the fusion process. Theimplant 200 may be further coated with bioactive fusion promotingsubstances including, but not limited to, hydroxyapatite compounds,osteogenic proteins and bone morphogenic proteins or may be frombioabsorbable material.

Referring to FIGS. 13-17, an alternative embodiment of the lordoticinterbody spinal fusion implant, generally referred to by the numeral300, is shown. The implant 300 is made of a mesh-like materialcomprising strands, which may be made of metal, that are pressedtogether and molded. The upper and lower surfaces 312 and 314 may beconvex and conform to the natural surface curvature of the end plates ofthe vertebrae. In addition, the entire implant 300 may be molded to ashape that conforms to the shape of the disc space created by theremoval of disc material from between two adjacent vertebrae. In thismanner, the implant 300 has curved upper and lower surfaces 312 and 314,a curved side wall 318 and chamfered edges 319.

Referring to FIG. 7A, the implant 300 is shown inserted in the directionof arrow A into the disc space D₁ between adjacent vertebrae V₁ and V₂.The implant 300 conforms to the endplates of the adjacent vertebrae V₁and V₂ as the upper and lower surfaces 312 and 314 are convex, and theside walls 318 are curved to conform to the natural curvature of thevertebrae V₁ and V₂. In this manner, the implant 300 has the samedimensions as the disc material removed from between the two adjacentvertebrae V₁ and V₂.

The implant 300 may be made wholly or in part of a solid material and/ora porous material, and/or a mesh-like material. The implant 300 may havea surface comprising of a porous material, a mesh-like material, or havea surface that is roughened. It is appreciated that the implant 300 maybe solid or may be partially hollow and include at least one internalchamber in communication with said upper and lower surfaces.

As shown in FIG. 17, the mesh-like material comprises strands that areformed and pressed together such that interstices 339, capable ofretaining fusion promoting material and for allowing for bone ingrowth,are present between the strands in at least the outer surface of implant300. Alternatively, it is appreciated that the implant 300 may be madeof a cancellous material, similar in configuration to human cancellousbone, having interstices allowing for bone ingrowth. As the implant 300may be made entirely or in part of the cancellous material, theinterstices may be present in the outer surface of the implant 300and/or within the entire implant to promote bone ingrowth and hold bonefusion promoting materials.

Referring to FIGS. 18-23 an alternative embodiment of the implant of thepresent invention, generally referred to by the numeral 400, isdisclosed. The implant 400 has a substantially rectangular shape havingupper and lower surfaces 412 and 414. The upper and lower surfaces 412and 414 support the adjacent vertebrae and are disposed in a convergingangular relationship to each other in the same manner described above.

The implant 400 has a width W that is substantially less than the widthof the implants 100-300 such that a series of such implants 400 are usedas the interbody spinal implant, each placed closely adjacent to oneanother to approximate the size of the removed disc. The size of theimplant 400 is approximately 26 millimeters in length and is wide enoughso that four of them will substantially fill the intervertebral space,depending on which vertebrae are fused.

In the performing of a posterior lumbar interbody fusion, it is notpossible to replace the removed portions of the disc, if a total nucleardiscectomy has been performed, with a single large implant as the,delicate dural sac containing the spinal cord and nerve roots covers atall times at least some portion of the posterior disc space. The use ofmodular implants 400 that are inserted separately into the disc space isappropriate in such case. The modular implants 400 being approximatelyas long as the depth of the disc material removed, but beingconsiderably narrower, such that they could be introduced into the discspace from the posterior aspect to either side of the dural sac, andthen realigned side to side with the disc space so that a number of themeach having a length consistent with the depth of the disc removed inthat area would in combination have a width equal to the width of thedisc material removed. As the disc spaces in the lumbar spine aregenerally lordotic, the insertion end 420 of the modular implants 400would have to be taller and less tall posteriorly at the trailing end430.

To introduce the modular implant 400 that is taller at its insertion end420 than the space available at the posterior aspect of the disc space,even when that disc space is optimally distracted, is problematic. Themodular implants 400 of provide two solutions to the problem. Themodular implants 400 may have a reduced size at their insertion end 420,including but not limited to, a bullet nose, a convexity, and a chamferto a smaller front surface. This then provides that the implant 400 hasan area small enough to be introduced into the posterior aspect of thedisc space when the disc space is adequately distracted and the contourof that specialized insertion end of the implant 400 is such that itthen allows for a ramping up of the adjacent vertebrae relative to theimplant 400 as the implant is advanced forward into the disc space.

Alternatively, or in combination with the above, since in the preferredembodiment the implants 400 are wedge-shaped in the side elevationalview when upright but are generally rectangular when viewed from the topplan view, these implants may be introduced into the disc space on theirside such that the side walls of the implants are adjacent to the endplates of the adjacent vertebrae. The implants 400 have a side-to-sidedimension that is less than the dimension through the insertion end ofthe implant 400 when upright. It is possible to easily insert theimplant 400 first on their side and then to use the insertion instrumentengaged to the implant 400 to rotate the implant ninety degrees into thefully upright position, once it has been fully inserted. Once inserted,the upper and lower surfaces 412 and 414 are adjacent to the endplatesof the adjacent vertebrae and create and maintain the desired angularrelationship of the adjacent vertebrae as the upper and lower surfaces412 and 414 of the implant 400 are angled with respect to each other.

The implant 400 has large openings 415 in the form of rectangular slotsfor holding fusion promoting materials to promote bone growth from thevertebrae through the upper and lower surfaces 412 and 414 and into theinterior of the implant 400. As the implant 400 is modular and more thanone is implanted at a time, the large openings 415 are also present inthe side walls 418 of the implant 400 to provide for bone growth fromone implant to another implant such that after successful fusion, themodular implants 400 are interconnected to form a single unit.

Referring to FIG. 21, the trailing end 430 of the implant 400 is shownhaving an insertion instrument engaging means comprising a rectangularslot 424 and threaded opening 426.

Referring to FIG. 23, an enlarged fragmentary view along line 23 of FIG.22 illustrating the surface configuration the implant 400 is shown. Thesurface configuration of the implant 400 is the same as the poroustexture 260 described above.

Referring to FIG. 24, an alternative embodiment of the lordoticinterbody spinal fusion implant of the present invention, generallyreferred to by the numeral 500, is shown. The implant 500 is a modularimplant and has a similar overall configuration as implant 400. Theimplant 500 instead of having slots 415 has an upper and lower surfaces512 and 514 that are capable of receiving and holding bone, or othermaterials capable of participating in the fusion process and/or capableof promoting bone ingrowth. In the preferred embodiment, the upper andlower surfaces 512 and 514 comprise a plurality of posts 540 that arespaced apart to provide a plurality of interstices 542 which are partialwells with incomplete walls capable of holding and retaining milled bonematerial or any artificial bone ingrowth promoting material. The implant500 may be prepared for implantation by grouting or otherwise coatingthe surface 538 with the appropriate fusion promoting substances.

Referring to FIGS. 28 and 29, an enlarged view of the upper surface 512of the implant 500 and a partial cross section thereof are shown. In thepreferred embodiment, the posts 540 have a head portion 544 of a largerdiameter than the remainder of the posts 540, and each of theinterstices 542 is the reverse configuration of the posts 544, having abottom 546 that is wider than the entrance 548 to the interstices 542.Such a configuration of the posts 540 and interstices 542 aids in theretention of bone material in the surface 538 of the implant 500 andfurther assists in the locking of the implant 500 into the bone fusionmass created from the bone ingrowth. As the bone ingrowth at the bottom546 of the interstices 542 is wider than the entrance 548, the boneingrowth cannot exit from the entrance 548 and is locked within theinterstice 542. The surface 538 of the implant 500 provides for animprovement in the available amount of surface area which may be stillfurther increased by rough finishing, flocking or otherwise producing anon smooth surface.

In the preferred embodiment, the posts 540 have a maximum diameter inthe range of approximately 0.1-2 mm and a height of approximately 0.1-2mm and are spaced apart a distance of 0.1-2 mm such that the interstices542 have a width in the range of approximately 0.1 to 2 mm. The postsizes, shapes, and distributions may be varied within the same implant.

It is appreciated that the implant 500 shares the same structure andfeatures of the implant 400 described above.

FIG. 30 is a side elevational view of a segment of the human spinalcolumn S shown in lordosis with an alternative embodiment of thelordotic spinal fusion implant referred to by the numeral 600, that isadjustable and expandable shown inserted in a space to restore andmaintain the correct anatomical alignment of the adjacent vertebrae. Theimplant 600 comprises a lower member 682 and an upper member 684 whichwhen fitted together form an essentially rectangular implant. The uppermember 684 and the lower member 682 have hollow portions that face oneanother and receive tapered wedges 686 and 688 that fit within thehollow portion of the upper and lower members 682 and 684. The upper andlower members 682 and 684 each have a wedged interior surface 689 a and689 b which are angled towards the interior of the implant 600. Thewedges 682 and 684 are such that at their large end, they are higherthan the combined hollow space between the upper and lower members 684and 682, and shallower at the other end than the hollow space betweenthe upper and lower members.

The wedges 686 and 688 have a central threaded opening 690 and 692 inalignment with each other for receiving threaded screw 694. As the screw694 is threaded into the opening 690, the wedges 686 and 688 abut theinterior sloped surfaces 689 a and 689 b of the upper and lower members682 and 684. As the screw 694 is turned, the wedges 686 and 688 aredrawn together, and the sloped portions of the wedges force the uppermember 682 away from the lower member 684. As the interior slopedsurfaces 689 a and 689 b have a greater slope near the trailing end 630,than near the insertion end 620, the upper and lower members 682 and 684are forced apart more at the insertion end 620 than at the trailing end630. As a result, the upper and lower members 682 and 684 are disposedat a converging angular relationship to each other and support theadjacent vertebrae V₁ and V₂ in the same angular relationship.

Referring to FIG. 31, an alternative embodiment of the implant of thepresent invention, generally referred to by the numeral 700, is shown.The implant 700 has movable projections, in the form of spikes 708,which are movable from a first position within the implant 700 to asecond position extending outside of the implant. The implant 700 is ofa generally rectangular configuration, having a top surface 702 and abottom surface 704 of the implant with slots 706 for permitting pivotalmember 707 having spikes 708 at their ends to project through said slots706. The spikes 708 are pinned at one end 710 within the implant 700.

The implant 700 has opposing wedge shaped members 712 and 714 having acentral threaded opening 716 for receiving a threaded screw 718 having ahead 720 and a slot 722. The wedges 712 and 714 are facing each other sothat upon turning of the screw 718, will the two wedges 712 and 714 aredrawn together to cause the spikes 708 to pivot about their end 710 andproject to the exterior of the implant 700 through the aligned slots706. The implant 700 may comprise a series of holes 724 on its surfacesfor promoting bone ingrowth and fusion.

In use, after the removal of the disc material, the implant 700 with thespikes 708 in their withdrawn position, is inserted into the disc space.Then the screw 718 is turned until the spikes 708 are forced to enterthe vertebrae and the implant 700 is thus held firmly in place.

While the invention has been described with regards to the preferredembodiment and a number of alternative embodiments, it is recognizedthat other embodiments of the present invention may be devised whichwould not depart from the scope of the present invention.

What is claimed is:
 1. An artificial interbody spinal fusion implant forinsertion within an implantation space formed across the height of adisc space between adjacent vertebral bodies of a human spine, thevertebral bodies having an anterior aspect and a posterior aspecttherebetween, said implant comprising: a leading end for insertion firstinto the disc space and a trailing end opposite said leading end, amid-longitudinal axis, and a depth along said mid-longitudinal axis; atop and a bottom between said leading and trailing ends adapted to spaceapart the adjacent vertebral bodies, a height between said top and saidbottom, said top and said bottom having at least one openingtherethrough, said openings being in communication with one another topermit for the growth of bone from adjacent vertebral body to adjacentvertebral body through said implant, said top and said bottom being inan angular relationship to each other along at least a portion of thedepth of said implant sufficient to maintain the adjacent vertebralbodies in an angular relationship to each other, said top and saidbottom each having an interior surface oriented toward one another, saidinterior surfaces being spaced apart to define a hollow interior incommunication with said openings; and opposite sides between said topand said bottom, and between said leading and trailing ends, a widthbetween said opposite sides, and a maximum width of said implant beinglarger than a maximum height of said implant.
 2. The implant of claim 1,wherein said implant includes an access opening for accessing saidhollow interior.
 3. The implant of claim 2, wherein said access openingis larger than the largest of said openings.
 4. The implant of claim 2,wherein said access opening is configured to permit insertion ofosteogenic material into said hollow interior.
 5. The implant of claim4, wherein said osteogenic material includes a fusion promotingmaterial.
 6. The implant of claim 4, wherein said osteogenic material isbone.
 7. The implant of claim 4, wherein said osteogenic material is amaterial other than bone.
 8. The implant of claim 2 further comprising acover for closing said access opening.
 9. The implant of claim 8,wherein said cover cooperatively engages said access opening.
 10. Theimplant of claim 9, wherein said cover comprises a slidable door. 11.The implant of claim 1, wherein said top and said bottom furthercomprise it least a second opening.
 12. The implant of claim 1, whereinat least one of said openings are approximately 1 mm to 3 mm indiameter.
 13. The implant of claim 1, wherein at least one of saidopenings is macroscopic in size.
 14. An artificial interbody spinalfusion implant for insertion within an implantation space formed acrossthe height of a disc space between adjacent vertebral bodies of a humanspine, the vertebral bodies having an anterior aspect and a posterioraspect therebetween, said implant comprising: a leading end forinsertion first into the disc space and a trailing end opposite saidleading end, a mid-longitudinal axis, and a depth along saidmid-longitudinal axis; a top and a bottom between said leading andtrailing ends adapted to be placed within the disc space to contact andsupport space apart the adjacent vertebral bodies, a height between saidtop and said bottom, said top and said bottom having at least oneopening therethrough, said openings being in communication With oneanother to permit for the growth of bone from adjacent vertebral body toadjacent vertebral body through said implant, said top and said bottombeing in an angular relationship to each other along at least a portionof the depth of said implant sufficient to maintain the adjacentvertebral bodies in an angular relationship to each other, said top andsaid bottom each having an interior surface oriented toward one another,said interior surfaces being spaced apart to define a hollow interior incommunication with said openings, and wherein at least one of saidopenings is microscopic in size.
 15. The implant of claim 1, wherein atleast one opening in said top and at least one opening in said bottomform a channel through said implant.
 16. The implant of claim 1, whereinsaid trailing end includes at least one perforation.
 17. The implant ofclaim 1 having a plurality of openings capable of retaining fusionpromoting material.
 18. The implant of claim 1, wherein said sides haveat least one aperture.
 19. The implant of claim 1, wherein said at leastone aperture is sized in the range of approximately 1 mm to 3 mm. 20.The implant of claim 18, wherein said at least one aperture is incommunication with said openings in said top and said bottom.
 21. Theimplant of claim 1, wherein the junctions of said sides and at least oneof said trailing end and said leading end are rounded.
 22. The implantof claim 1, wherein said sides are generally parallel to one another.23. The implant of claim 1, wherein said sides are generally flat. 24.The implant of claim 1, wherein said sides are curved.
 25. The implantof claim 1, wherein the shape of said sides is generally trapezoidal.26. The implant of claim 1, wherein said implant is configured togenerally taper from said trailing end to said leading end.
 27. Theimplant of claim 1, wherein each of said top and bottom have a lengthgreater than the depth of said implant along the mid-longitudinal axis.28. The implant of claim 1, wherein said implant is a wedge.
 29. Theimplant of claim 1, wherein said implant has a width that isapproximately 32 mm for use in the lumbar spine.
 30. The implant ofclaim 1, wherein said implant has a width in the range of approximately28 mm to 48 mm for use in the lumbar spine.
 31. The implant of claim 1,wherein said implant has a generally rectangular cross sectiontransverse to the mid-longitudinal axis along at least a portion of itsdepth.
 32. The implant of claim 1, wherein said leading end is at leastin part curved.
 33. The implant of claim 1, wherein at least a portionof said leading end is tapered for facilitating insertion of saidimplant between the two adjacent vertebral bodies.
 34. The implant ofclaim 1, wherein said leading end is curved.
 35. The implant of claim34, wherein said leading end generally conforms to the disc spaceproximate the posterior aspect of the vertebral bodies.
 36. The implantof claim 1, wherein said leading end is convex.
 37. The implant of claim1, wherein said trailing end is curved.
 38. The implant of claim 1,wherein said trailing end is convex.
 39. The implant of claim 1, whereinthe maximum depth of said implant is less than the posterior to anteriordepth of the end plates of the adjacent vertebral bodies.
 40. Theimplant of claim 1, wherein said implant is adapted for insertion fromthe anterior aspect of the vertebral bodies.
 41. The implant of claim 1,wherein said implant is sized to replace a substantial portion of thedisc with a single implant.
 42. The implant of claim 1, wherein saidimplant has substantially the same shape as a space created by theremoval of at least a substantial portion of the nucleus pulposus and aportion of the annulus fibrosus from between the two adjacent vertebralbodies.
 43. The implant of claim 1, wherein said implant has a heightsubstantially equal to the height of the space created by the removal ofdisc material from between the adjacent vertebral bodies.
 44. Theimplant of claim 1, wherein said implant has substantially the sameheight, width and depth as a space created by the removal of at leastgenerally the nucleus pulposus and at least a portion of the annulusfibrosus from between the two adjacent vertebral bodies.
 45. The implantof claim 1, wherein said implant dimensionally corresponds to the spacecreated by the removal of at least generally all of the nucleus pulposusand a portion of the annulus fibrosus when said adjacent vertebralbodies are distracted and placed in angular relationship to each other.46. The implant of claim 1, wherein the depth of said implant is in therange of approximately 11 mm to 21 mm for use in the cervical spine. 47.The implant of claim 1, wherein the width of said implant is in therange of approximately 14 mm to 28 mm for use in the cervical spine. 48.The implant of claim 1, wherein said implant has the maximum height inthe range of approximately 5 mm to 10 mm, the maximum width in the rangeof approximately 14 mm to 28 mm, and a depth in the range ofapproximately 11 mm to 21 mm for use in the cervical spine.
 49. Theimplant of claim 1 for use in the lumbar spine, wherein the depth of aidimplant is in the range of approximately 20 mm to 34 mm.
 50. The implantof claim 1, wherein said implant has the maximum height in the range ofapproximately 8 mm to 16 mm, the maximum width in the range ofapproximately 28 mm to 48 mm, and depth in the range of approximately 20mm to 34 mm for use in the lumbar spine.
 51. The implant of claim 1,wherein the depth of said implant is substantially the same as the depthof a space created by the removal of the nucleus pulposus from betweenthe two adjacent vertebral bodies.
 52. The implant of claim 1, whereinthe width of said implant is substantially equal to the transverse widthof a space created by the removal of the nucleus pulposus from betweenthe two adjacent vertebral bodies.
 53. The implant of claim 1, whereinsaid top has a fixed shape which is generally configured to match thecontours of the endplate of one of the two adjacent vertebral bodies.54. The implant of claim 1, wherein said bottom has a fixed shape whichis generally configured to match the natural contours of the endplate ofone of the two adjacent vertebral bodies.
 55. The implant of claim 1,further comprising at least one protrusion extending from said top andsaid bottom for engaging the adjacent vertebral bodies to maintain saidimplant within the disc space.
 56. The implant of claim 55, wherein saidprotrusion comprises a ridge.
 57. The implant of claim 55, wherein saidprotrusion comprises a plurality of ridges facing the same direction toprevent expulsion of said implant in a direction opposite to said samedirection.
 58. The implant of claim 55, wherein said protrusioncomprises a tooth.
 59. The implant of claim 55, wherein said protrusioncomprises a ratchet.
 60. The implant of claim 59, wherein saidprotrusion comprises a plurality of ratchets facing the same directionto prevent expulsion of said implant in a direction opposite to saidsame direction.
 61. The implant of claim 1, further comprising anirregular surface for engaging the adjacent vertebral bodies and formaintaining said implant in place, said irregular surface being presenton at least a part of said top and said bottom.
 62. The implant of claim61, wherein said irregular surface comprises at least one groove. 63.The implant of claim 61, wherein said irregular surface includesknurling.
 64. The implant of claim 61, wherein said irregular surfaceincludes at least one spike.
 65. The implant of claim 1, furthercomprising a plurality of surface roughenings for engaging said adjacentvertebral bodies and for maintaining said implant in place, said surfaceroughenings being present on at least a portion of said top and saidbottom.
 66. The implant of claim 65, wherein said roughenings coversubstantially the entire top and bottom of said implant, saidroughenings being generally tapered from said trailing end to saidleading end.
 67. The implant of claim 65, herein a height of eachroughening measured from the mid-longitudinal axis of the implantdecreases from said trailing end to said leading end.
 68. The implant ofclaim 65, wherein said surface roughenings comprise at least one groove.69. The implant of claim 1, wherein said top and said bottom have a boneingrowth surface.
 70. The implant of claim 1, wherein said implant hasan exterior surface that is at least in part porous.
 71. The implant ofclaim 1, wherein said implant comprises a mesh-like material having aplurality of interstices for receiving fusion promoting material. 72.The implant of claim 1, wherein said implant is porous.
 73. Anartificial interbody spinal fusion implant for insertion within animplantation space formed across the height of a disc space betweenadjacent vertebral bodies of a human spine, the vertebral bodies havingan anterior aspect and a posterior aspect therebetween, said implantcomprising: a leading end for insertion first into the disc space and atrailing end opposite said leading end, a mid-longitudinal axis, and adepth along said mid-longitudinal axis; a top and a bottom between saidleading and trailing ends adapted to space apart the adjacent vertebralbodies, a height between said top and said bottom, said top and saidbottom having at least one opening therethrough, said openings being incommunication with one another to permit for the growth of bone fromadjacent vertebral body to adjacent vertebral body through said implant,said top and said bottom being in an angular relationship to each otheralong at least a portion of the depth of said implant sufficient tomaintain the adjacent vertebral bodies in an angular relationship toeach other, said top and said bottom each having an interior surface,said interior surfaces being spaced apart to define a hollow interior incommunication with said openings; opposite sides between said top andsaid bottom, and between said leading and trailing ends, a width betweensaid opposite sides, and a maximum width of said implant being largerthan a maximum height of said implant; and an exterior surface, at leasta portion of which is treated to promote bone ingrowth between saidsurface and a vertebral body.
 74. The implant of claim 1, in combinationwith a fusion promoting material other than bone at least in part withinsaid hollow interior.
 75. The implant of claim 1, wherein said implantcomprises a bone ingrowth material other than bone.
 76. The implant ofclaim 1, further comprising a material that intrinsically participatesin the growth of bone from one of the adjacent vertebral bodies to theother of the adjacent vertebral bodies.
 77. The implant of claim 1,wherein said implant is treated with a fusion promoting substance. 78.The implant of claim 77, wherein said fusion promoting substance isautogenous bone.
 79. The implant of claim 1, wherein said implant isstronger than bone.
 80. The implant of claim 1, further in combinationwith an osteogenic material at least in part within said hollowinterior.
 81. The implant of claim 80, wherein said osteogenic materialis a material other than bone.
 82. The implant of claim 1, wherein saidimplant comprises a bone ingrowth material for promoting bone ingrowthbetween said implant and said two adjacent vertebral bodies.
 83. Thespinal fusion implant of claim 1, wherein said implant is at least inpart bioresorbable.
 84. The implant of claim 1, wherein said implant isadapted to be centrally placed within the disc space.
 85. The implant ofclaim 1, wherein at least one of said leading and trailing ends of saidimplant is configured to engage a driving instrument for implanting saidimplant within the disc space between the two adjacent vertebral bodies.86. The implant of claim 1, further comprising an expander moving saidtop and bottom apart in said diverging angular relationship.
 87. Theimplant of claim 1, wherein said trailing end has a height greater thansaid leading end.
 88. The implant of claim 1, wherein at least one ofsaid top and bottom is substantially flat.
 89. The implant of claim 88,further comprising an irregular surface for engaging the adjacentvertebral bodies and for maintaining said implant in place, saidirregular surface being present on at least a part of said top and saidbottom.
 90. The implant of claim 89, wherein said irregular surfacecomprises at least one groove.
 91. The implant of claim 89, wherein saidirregular surface includes knurling.
 92. The implant of claim 88,further comprising a plurality of surface roughenings for engaging saidadjacent vertebral bodies and for maintaining said implant in place,said surface roughenings being present on at least a portion of said topand said bottom.
 93. The implant of claim 92, wherein said rougheningscover substantially the entire top and bottom of said implant, saidroughenings being generally tapered from said trailing end to saidleading end.
 94. The implant of claim 1, wherein at least one of saidtop and bottom is generally planar.
 95. The implant of claim 94, furthercomprising an irregular surface for engaging the adjacent vertebralbodies and for maintaining said implant in place, said irregular surfacebeing present on at least a part of said top and said bottom.
 96. Theimplant of claim 95, wherein said irregular surface comprises at leastone groove.
 97. The implant of claim 95, wherein said irregular surfaceincludes knurling.
 98. The implant of claim 94, further comprising aplurality of surface roughenings for engaging said adjacent vertebralbodies and for maintaining said implant in place, said surfaceroughenings being present on at least a portion of said top and saidbottom.
 99. The implant of claim 98, wherein said roughenings coversubstantially the entire top and bottom of said implant, saidroughenings being generally tapered from said trailing end to saidleading end.
 100. The implant of claim 1, wherein each of said top andbottom are substantially flat.
 101. The implant of claim 100, furthercomprising an irregular surface for engaging the adjacent vertebralbodies and for maintaining said implant in place, said irregular surfacebeing present on at least a part of said top and said bottom.
 102. Theimplant of claim 101, wherein said irregular surface comprises at leastone groove.
 103. The implant of claim 101, wherein said irregularsurface includes knurling.
 104. The implant of claim 100, furthercomprising a plurality of surface roughenings for engaging said adjacentvertebral bodies and for maintaining said implant in place, said surfaceroughenings being present on at least a portion of said top and saidbottom.
 105. The implant of claim 104, wherein said roughenings coversubstantially the entire top and bottom of said implant, saidroughenings being generally tapered from said trailing end to saidleading end.
 106. The implant of claim 1, wherein each of said top andbottom are generally planar.
 107. The implant of claim 106, furthercomprising an irregular surface for engaging the adjacent vertebralbodies and for maintaining said implant in place, said irregular surfacebeing present on at least a part of said top and said bottom.
 108. Theimplant of claim 107, wherein said irregular surface comprises at leastone groove.
 109. The implant of claim 107, wherein said irregularsurface includes knurling.
 110. The implant of claim 106, furthercomprising a plurality of surface roughenings for engaging said adjacentvertebral bodies and for maintaining said implant in place, said surfaceroughenings being present on at least a portion of said top and saidbottom.
 111. The implant of claim 110, wherein said roughenings coversubstantially the entire top and bottom of said implant, saidroughenings being generally tapered from said trailing end to saidleading end.
 112. The implant of claim 1, wherein said implant has agenerally quadrilateral cross section transverse to the mid-longitudinalaxis along at least a portion of its depth.
 113. The implant of claim 1,wherein said implant is sized to replace a substantial portion of thedisc with a single implant.
 114. The implant of claim 1, in combinationwith a fusion promoting substance at least in part within said hollowinterior.
 115. The spinal fusion implant of claim 114, wherein saidfusion promoting substance includes at least one of bone, bonemorphogenetic protein, hydroxyapatite, and hydroxyapatite tricalciumphosphate.
 116. An artificial interbody spinal fusion implant forinsertion within a disc space between adjacent vertebral bodies of ahuman spine, the vertebral bodies having an anterior aspect and aposterior aspect, said implant comprising: a leading end for insertionfirst into the disc space and a trailing end opposite said leading end,a mid-longitudinal axis, and a depth along said mid-longitudinal axis; atop and a bottom between said leading and trailing ends adapted to beplaced within the disc space to contact and support the adjacentvertebral bodies, said top and said bottom having at least one openingtherethrough, said openings being in communication with one another topermit for the growth of bone from adjacent vertebral body to adjacentvertebral body through said implant, said top and said bottom being inan angular relationship to each other along at least a portion of thedepth of said implant sufficient to maintain the adjacent vertebralbodies in an angular relationship to each other, each of said top andsaid bottom having an interior surface, said interior surfaces beingspaced apart to define a hollow interior in communication with saidopenings; opposite sides between said top and said bottom, and betweensaid leading and trailing ends; an access opening for accessing saidhollow interior; and a cover for closing said access opening, said covercooperatively engaging said access opening, said cover including asurface deviation to facilitate opening and closing of said accessopening with said cover.